Bilayer-Spanning DNA Nanopores with Voltage-Switching between Open and Closed State

• Published in: ACS nano 2015-02, Vol.9 (2), p.1117-1126
• Main Authors: Seifert, Astrid, Göpfrich, Kerstin, Burns, Jonathan R, Fertig, Niels, Keyser, Ulrich F, Howorka, Stefan
• Format: Article
• Language: English
• Subjects: Cell Membrane - chemistry; Cell Membrane - metabolism; DNA - chemistry; Electric Conductivity; Lipid Bilayers - chemistry; Lipid Bilayers - metabolism; Molecular Conformation; Nanopores; Polyethylene Glycols - chemistry
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/nn5039433

Membrane-spanning nanopores from folded DNA are a recent example of biomimetic man-made nanostructures that can open up applications in biosensing, drug delivery, and nanofluidics. In this report, we generate a DNA nanopore based on the archetypal six-helix-bundle architecture and systematically characterize it via single-channel current recordings to address several fundamental scientific questions in this emerging field. We establish that the DNA pores exhibit two voltage-dependent conductance states. Low transmembrane voltages favor a stable high-conductance level, which corresponds to an unobstructed DNA pore. The expected inner width of the open channel is confirmed by measuring the conductance change as a function of poly(ethylene glycol) (PEG) size, whereby smaller PEGs are assumed to enter the pore. PEG sizing also clarifies that the main ion-conducting path runs through the membrane-spanning channel lumen as opposed to any proposed gap between the outer pore wall and the lipid bilayer. At higher voltages, the channel shows a main low-conductance state probably caused by electric-field-induced changes of the DNA pore in its conformation or orientation. This voltage-dependent switching between the open and closed states is observed with planar lipid bilayers as well as bilayers mounted on glass nanopipettes. These findings settle a discrepancy between two previously published conductances. By systematically exploring a large space of parameters and answering key questions, our report supports the development of DNA nanopores for nanobiotechnology.